"You'll need a new app to open this file" is probably the most common error faced by millions of Windows users every day. This is either because the program required to open a file is not available on your system or there may be other issues.

What is .D2S file extension?

Game file created by Diablo II, an action role-playing game; saves character, item, and progress information for the player; includes stats, inventories, waypoints, skills, quests, mercenaries, and other information; saved automatically by the game.
D2S files can be edited manually using Hero Editor.
You can see a list of software programs here on easyfileopener.org that can open this file type so that you don’t need to search for it on the web. You can then open your file with this extension using a software listed below.